Standard enthalpies of formation of some thulium alloys by high temperature direct synthesis calorimetry.

The standard enthalpies of formation of some Thulium alloys in the binary s ystems of Tm-X (where X=C, Si, Ge, Sn, B, Ga) have been determined by high temperature direct synthesis calorimetry at 1373+/-2 K. The following value s of Delta H-f(degrees) in kJ/mol of atoms are reported: TmC2 = -31.5 +/- 2 .5; TmSi = -86.1 +/- 2.3; Tm5Si3=-76.1 +/- 2.3; TmSi2 = -64.9 +/- 2.8; Tm5G e3 = -91.3 +/- 1.9; Tm5Sn3 = 72.8 +/- 2.1; TmB2 = -30.6 +/- 3.0; TmGa3 = -4 8.5 +/- 2.0. The results are compared with earlier experimental data, with available data for the corresponding compounds of neighbouring lanthanide e lements and with predicted values from the semi-empirical model of Miedema and co-workers [Niessen et al., Calphad 1983,7:51-70]. (C) 1999 Elsevier Sc ience S.A. All rights reserved.